Expansion joint



July 10, 1962 G. F. DAVEY- EXPANSION JOINT 2 Sheets-Sheet 1 Filed Feb. 26, 1957 G. F. DAVEY EXPANSION JOINT July 10, 1962 2 Sheets-Sheet 2 Filed Feb. 26, 1957 INVENTOR. GERALD F. DH l/EY Unite This invention relates to an expansion joint and more particularly to a means for providing a gas-tight, hightemperature connection for use in furnaces, ducts, and the like.

In industries which make use of high temperature gases and the like, a considerable problem is presented by the fact that enclosures must be constructed in such a manner that they are gas-tight and yet capable of expansion and contraction with changes of temperature. This is true, for instance, in the case of the furnace associated with a steam generating unit, which furnace in many cases may involve considerable wall areas and, thus, considerable amounts of expansion and contraction. In the same way, the expansion and contraction of long metal ducts containing gases of varying temperatures presents considerable difficulties because of the possibility of buckling. Attempts have been made in the past to solve this problem by the use of fittings of various shapes and configurations in the joints. Such fittings are subject to fatigue failure and eventual leakage of gas and in some situations are very expensive. These and other deficiencies of the prior art have been obviated in a novel manner by the present invention.

It is therefore an outstanding object of the present invention to provide an expansion joint for joining two sheet metal members, which joint is gas tight and fully capable of permitting free motion of the sheet metal members.

Another object of this invention is the provision of the expansion joint which is inexpensive to manufacture, easy to maintain, and is capable of a long life of useful service.

It is a still further object of the present invention to provide an expansion joint making use of a semi-fluid, gas seal.

A still further object of the instant invention is the provision of an expansion joint capable of operation at wide extremes of temperatures.

Another object of this invention is the provision of an expansion joint formed of substances which are not subject to chemical attack or erosion.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself as to its objects and advantages, the mode of its operation and the manner of its organization may be understood by referring to the following description, taken in connection with the accompanying drawings, forming a part thereof, in which:

FIGURE 1 is a sectional view of a furnace wall embodying the principles of the present invention, and

FIGURE 2 is a sectional view of the wall of a duct making use of the invention.

Referring to FIGURE 1 the expansion joint, designated generally by the reference numeral 10, is shown in use in association with the wall 11 of a furnace. In this particular showing the furnace is part of a steam generating unit and includes parallel water well tubes 12 arranged with a slight space therebetween. A sheet 13 of expanded metal is tackwelded to the side of the tubes facing away from the furnace interior. This sheet forms an anchoring means to lock in place a layer 14 of plastic refractory overlying the back surfaces of the $343,055 Patented July 10, 1962 tubes and extending into the spaces therebetween. Next to the outer flat surface of the layer 14 of plastic refractory is placed a layer 15 of block insulation having interlocking joints to hold them together. Over the other surface of the layer 15 is'placed a blanket 16 of wall type insulation. Covering the exterior of the wall described above and holding the blanket 16 in place, is a casing 17 consisting of a plurality of large steel sheets 18 and 19 and so on. At every position where the steel sheets abut each other an expansion joint 10 is provided. In the embodiment of the invention shown, the steel sheets 18 and 19 are jointed by the expansion joint 10 in the manner shown.

The expansion joint lticomprises an inner member 21 and an outer member 27 between which the sheets 18 and 19 are clamped. Both the inner and outer member extend longitudinally along the edges of the sheets a considerable distance in a direction at right angles to the plane of the drawing. The inner member 21 consists of an elongated steel strip wide enough to overlapthe edges of the sheets 18 and 19 a considerable distance. The inner member extends transversely away from the edges of the sheets by an amount at least equal to the amount by which the outer member so extends, so that there is little or no force couple on the edge of the sheets to inhibit free sliding action. To the flat surface that contacts the sheets in the central portion thereof are fas? tened by welding a number of studs, similar to the stud 23, each having a threaded outer end adapted to receive a washer 24 and a nut 25. The outer member 22 consists of an elongated channel member having a central web 26 and inwardly directed flanges, 27 and 23. The central web 26 is provided at intervals with circular apertures 29 situated to permit the passage therethrough of the stud 23. It can be seen then that the action of the nut 25 is to cause the inner and outer members to clamp the edges of the sheets 18 and 19. A central web 26 and the flanges 27 and 28 of the outer member 22 define an inner chamber 31 in which is located a body 32 of mastic. This mastic is of the type designed for use at about 400 degrees Fahrenheit and consists of a mixture of asphalt and powdered asbestos. Extending through the flange 27, is a fitting 33, which may be similar to the well-known Zerk fitting adapted to permit the introduction of mastic into the chamber 31 by use of a grease gun. The fitting consist of a generally tubular main body 34, threaded into an aperture in the flange 27 and having on its outer end an inwardly directed flange defining a small aperture 35. A ball 36 is pressed against the inner surface of the aperture by a coil spring 37. A flange 28 of the outer member is provided with an air-release member 38 consisting of a tubular mom-j ber 39, threaded into an aperture in the flange and having external threads at its outer end. A cap 41 is threaded on the said outer end and serves as a closure therefor.

The operation of the apparatus will be readily understood in view of the above description. In the operation of the furnace, there is usually a pressure differential between the inside and the outside. In the present case, let us suppose that the furnace is pressurized,that is to say, the pressure on the inside of the furnace is greater than that on the outside. T here will be a seepage of gas through the elements of the furnace wall 11 which will be largely uninhibited by the layers of insulation. The casing 17, being made of steel, is relatively impervious and prevents a leakage of gas, except where a joint occurs. In the present case, the leakage of gas around the edges of the sheets 18 and 19 is prevented by the presence of the mastic therein. The mastic is introduced into the chamber 31 by means of a grease gun under considerable pressure. Of course, as the furnace is brought from a cold condition to a hot conv the inner surfaces of these members.

dition, these sheets 18 and 19 expand and the edges thereof tend to come together or to draw apart, depending on the particular part of the furnace in which the joint is located.

Although the inner and outer members of the expansion the joint. At higher temperatures, of course, the mastic will be of a lower viscosity but the proper selection of mastic will insure that the viscosity never will be low enough to permit the passage of gas thereby. When the mastic is introduced through the fitting 33 it is necessary that some means he provided for the removal of the air residing in the chamber, and this function is served by the member 38. The member 38 also provides a means of inspecting the interior of the chamber.

FIGURE 2 illustrates the manner in which the invention can be applied to a duct through which heated gas may pass. Problems presented by a duct, of course, are somewhat more complicated than those presented by the case in the furnace wall, since in the case of the furnace wall, movement of the sheets at the joint is probably in one plane only. In the case of a duct, the portions of the duct connected by the joint may move relative to each other in several modes as will be explained fully hereinafter. The expansion joint 110 is shown in use with a duct 111 and with an auxiliary joint member 112 associated therewith. For the purpose of illustration let'us assume that the duct 111 is a circular craft section, and consists of 2 portions 113 and 114, whose ends are somewhat separated. A sheet metal shield 115 is tack-welded to the end of the portion 113 while a similar shield 116 is similarly fastened to the end of the portion 114. These shields incline upwardly toward one another to form conical portions 117 and 118 which are provided at their outermost portions with radial flanges 119 and 121, respectively. Suflicient resilience is provided in the flanges 119 and 121 to assure that they slide and contact each other despite the normal movements of the portions 113 and 114. Welded to the portion 114 is a ring122 to which is fastened a housing member 123. This housing member is provided with a, curved portion 124 whose surface extends from the ring 122 outwardly and longitudinally of the duct to a point overlying the portion 113 of the duct, at which point is formed a radially inwardly-directed flange portion 125. A channel-like ring 126 to which is welded a radiallydii'ected sheet metal ring 127. Edges of the ring 127 and the inwardly directed flange 125 reside adjacent to each other but are somewhat spaced to form an annular space extending entirely around the duct. The housing 123 and the shields 115 and 116 form a chamber 128 withinwhich resides an asbestos cloth bag 129 which conforms closely to with a body 131 of bulk insulation. 7 g

The expansion joint 110 consists of an inner member "132 and an outer member 133. The inner member is of a flat, sheet metal construction, and in the case of a circu- "lar duct would, of course, be an annular ring. 7 At spaced intervals; the inner member has attached in the central 'portion thereof'studs 1 34, each having a threaded outer end adapted to -receive a Washer 135 and a nut 1 36. The

' inner side of the inner member 132 is welded to the outer edge of the ring 127 and is fixed thereto. The outer mem:

her 133 has a generally channel-shaped cross-section'and, in the case ofa circular duct, would be annular; it is provided with a central web 137 and longitudinally extending flanges 138 and 139. The flange 139 which is 139 of the outer member 133 define with the edges of the flange 125 and the ring 127 a chamber 142 in which resides a body 143 of the type of mastic described in connection with the apparatus of FIGURE 1. At suitable intervals on the outer member are provided fitting members 144 for the admission of mastic into the chamber 142 bymeans of a grease gun. A suitable air vent and inspection member 145 extends through the central web 137 at suitable intervals.

The operation of this embodiment of the invention is very similar to that described in connection with the species shown in FIGURE 1. However in this case, it will be observed that the inner and outer members of the expansion joint are fastened to the portion 113 of the duct and the The bag 129 is filled only motion which takes place relative thereto is that of the flange 125 which moves in and out according to the positioning of the portion 114 of the duct. Movement of the portions of the duct toward and away from one another are taken up in the housing 123 and movement in a bending manner, i.e., changes in angulan'ty of the portions 113 and 114, will be absorbed in the same manner. Transverse movement of the portions 113 and 114, i.e., sideways dislocation thereof, will be absorbed intheexpansion joint, and, as a matter of fact, the other modes of relative motion of the portions involve a certain amount of lateral dislocation which will also be absorbed in the expansion joint. For instance, in the case of bending motion, i.e., angular dislocation of the portions of the duct, the flange 125 will be drawn away from the portion 113 at one side and will move inwardly'toward it on the other side. Both of these motions will be permitted by the use of the expansion joint of the invention. The shields 115 and 116 tend to prevent the transmission of heat into the outer portions of the joint, but they do not tend to prevent leakage of gas to any great extent. Cloth bag 129 and the body of insulation 131 absorb vibrations and tend to dampen any motions that take place, but they do not present an appreciable obstacle to the leakage of gas; it is the expansion joint which provides this function.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

The invention having been best described, what is claimed is new and desired to secure by patent is:

1. An expansion joint for use with sheet metal enclosures containing gas under a pressure differential and subject to extreme temperature variations, comprising an inner member, an outer member, means for drawing the -members together to clamp adjacent edges of the en- 'closurebetween them, the inner member extending transversely away from the said edges of the enclosure by an amount at least equal to .the' amount by which the outer member so extends, the members defining a chamber Within which the edges reside, a body of thermo-plastic mastic residing in the chamber, themastic being in a plastic state at the normal operating temperature of the joints, and means for introducing mastic into the chamber under pressure to allow expansion and contraction of the enclosure without leakage of gas. V I

2. An expansion joint for use with the sheet metal casing of a furnace containing gas under pressure and subject to'extreme temperature variations, comprising an inner member, an outer member of channel form, a screw fastening for drawing the members together to clamp adjacent edges of the enclosure between them, the inner member .extending transversely away from'the edges of the enclosure by an amount at least equal to the amount by which the outer member so extends, the outer member defining a chamber in which the edges reside, a body of thermoplastic mastic residing in the chamber, the mastic being in a plastic state at the normal operating temperature of the joint, and a fitting extending through the outer'mernber for introducing mastic into the chamber under pressure to allow expansion and contraction of the enclosure without leakage of gas.

3. An expansion joint for a pressurized furnace, comprising a casing formed of sheets of metal having edges adjacent one another, an inner member, an outer member of channel form having two inwardly-directed flanges, the inner member extending transversely away from the edges of the sheets by an amount at least equal to the amount by which the outer member so extends, means drawing the members toward one another so that the edge of one sheet is clamped between one flange and the inner member and the edge of the other sheet is clamped between the other flange and the inner member, the outer member and the sheets defining a chamber, a fitting extending through the outer member for introducing a high-temperature thermoplastic mastic into the chamber under pressure to allow expansion and contraction of the sheets without leakage of gas.

4. An expansion joint for a duct containing gas under pressure and subject to extreme temperature variations, comprising two generally aligned duct portions having their ends spaced from one another, an outwardly-extending sheet metal ring extending from one portion, a housing member attached to the other portion and having an inwardly-directed sheet metal flange, the edges of the ring and flange residing adjacent one another, an inner member, an outer member, the inner member extending transversely away from the edges of the flanges by an amount at least equal to the amount by which the outer member so extends, means drawing the members toward one another to clamp the edges of the ring and the flange therebetween, the members defining a chamber in which the said edges reside, and a fitting extending through one of the members for introducing into the chamber a high-temperature thermo-plastic mastic under pressure to allow expansion and contraction of the enclosure without leakage of gas.

References Cited in the file of this patent UNITED STATES PATENTS Re. 21,524 Gramelspacher Aug. 6, 1940 2,226,201 Freyssinet Dec. 24, 1940 2,655,238 Langvand Oct. 13, 1953 2,727,286 Moore Dec. 20, 1955 FOREIGN PATENTS 744,723 Great Britain Feb. 15, 1956 

